A response time of a disk for an input/output (Input/Output, I/O for short) request becomes longer because of magnetic degradation, a bad sector, vibration, or another mechanical or environmental problem of the disk. This type of disk that is extremely slow in responding to an I/O request is referred to as a slow disk.
The slow disk is a major threat to reliability of a storage system. Particularly, for a redundant array of independent disks (Redundant Arrays of IndependentDisks, RAID for short) and a distributed storage system, a slowdown of one disk may cause performance degradation of a total system, and even cause service interruption in a severe case. Therefore, the disk needs to be detected, so as to take a corresponding processing measure in a timely manner, for example, to isolate the slow disk and perform data backup.